Advanced Materials Research Vols. 1073-1076

Abstract: In the Pb²⁺ stress experiments, the concentrations of Pb²⁺ were 1, 5, 10, 50, and 80 mg/L respectively, BG11 culture medium was served as the control. The results showed that Pb²⁺ affected markedly on the growth and physiological characteristics of chlorella pyrenoidosa under certain concentration. As the exposure time, chlorella pyrenoidosa biomass is restrained gradually. Pb²⁺ also have significant inhibition to effect chlorophyll content and have an effect relationship with the malondialdehyde content of chlorella pyrenoidosa . Lead concentrations and the soluble protein content are time effect relationship . And the longer the inhibitory effect becomes more obvious. Superoxide dismutase (sod) activity increased first then decreased with the increase of the concentration of Pb²⁺.

Abstract: N₂O is an important greenhouse gas. The emission of N₂O in wetlands is an important part of global N₂O flux. At present, the two leading factors mainly focus on the emission regularity of N₂O and the emission mechanism of it in the estuary wetland ecosystem at home and abroad. The main sources of wetland N₂O are the soil nitrification and denitrification. Research shows that, the N₂O emission is directly related to the availability of the soil nitrogen and the salinity reduces the production of N₂O by restraining the soil nitrification and denitrification process. Therefore, it is necessary to strengthen the study on the emission characteristics and influence factors of N₂O in the coastal wetland.

Abstract: Microbial conversion is a key process in the biosynthetic routes of steroid medicine.The whole process of bioconversion includes two essential steps: (1) enzymatic reaction step where the enzyme-catalyzed substrate transformation takes place inside the cells, and (2) diffusion step that includes the diffusion of substrate molecules from the surface of solid substrate particles into bulk media (i.e., the solubilization of solid substrate), the diffusion of solubilized substrate molecules from bulk media into cells, and the diffusion of formed product molecules from inside cells into bulk media. In this review, the applications of three chemical factors (growth regulator,surfactant and cyclodextrin), and their effects on steroid microbial enzymatic conversion were extensively discussed, which provides insights into the development of novel approaches to cost-effectively improve biosynthesis efficiency in steroid medicine.

Abstract: Flow pattern and mode have a far influence on the efficiency of biological treatment systems. In order to investigate the effects of different flow patterns on the growth of Bacillus subtilis, a self-developed fluid mixing device was designed to produce different liquid fluidization. It was found that the greater Re, the more conducive to the growth of bacteria, which evidenced by the logarithmic phase shorter and reached stationary phase bacteria concentration increased; when the Reynolds number is low, growth curve of Bacillus subtilis appeared Growth - stationary - growth and cell precipitation phenomenon, both phenomena gradually disappeared when Re increases. Besides, it can consume dissolved oxygen after inoculation with Bacillus subtilis, which keeping the dissolved oxygen in the medium at a lower level (0~1mg/L)

Abstract: Eupatorium adenophorum (croftonweed), one of the most destructive alien species in China, has been demonstrated or indicated to have inhibitory effects on other species in laboratory bioassay. However, allelopathic compounds of E. adenophorum may play other roles more than interspecific interference. Here we investigated whether E. adenophorum aqueous leachates could influence conspecific seed germination and seedling growth with laboratory bioassay and found that it could inhibit seed germination and reduce seedling root elongation of E. adenophorum. Then we examined interactions between E. adenophorum leachate and natural soil on germination and seedling growth of E. adenophorum itself. The results showed that soil from different habitats altered the allelopathic effects usually observed in laboratory bioassay. In the heavily invaded site, E. adenophorum were inhibited by E. adenophorum leachates; whereas, in two lightly invaded sites, germination and seedling growth of E. adenophorum was significantly facilitated. We can infer that allelochemicals from E. adenophorum play a dramatic role in regulating its population density.

Abstract: The aims of the present work were simulating actual environmental pollution to select and compare the bacterial communities under different environmental stresses such as phenanthrene and pyrene. Two bacterial consortia named as Phe consortium and Pyr consortium were enriched from activated sludge obtained from a wastewater treatment plant. The PCR-DGGE analysis showed that the original active sludge harbored abundantly diverse PAH-degrading bacteria at first, then under different environmental pressures the consortium species tended to be concentrated and had species structure differences. In addition, the abilities of the two bacterial consortia to remediate a mixture of 4 PAHs (50 mg Kg^-1 each) in soil were studied. Of the 4 PAHs, greater than 80% of the fluorene and phenanthrene in soil were removed by the Phe consortium in just 7-days respectively; whereas the Pyr-consortium could degrade over 60% of anthracene and pyrene.

Abstract: In order to achieve lactic acid bacteria (LAB) with high antioxidant activity and provide a theoretical reference for the development of natural antioxidants, 8 stains of LAB were studied by hydroxyl radical scavenging experiments, DPPH and hydroxyl radical assays, anti-lipid peroxidation assays and reducing powder evaluation experiments. The results showed that the antioxidant capabilities of the 8 strains of LAB were quite different and the fermentation supernatant had better antioxidant activity than the intact cell and the intracellular extracts. Moreover, Lb,Lr and Lm₁ strains demonstrated better capacity on antioxidant activity than others, which could be considered as potential antioxidant strains to be applied in functional foods.

Abstract: Biofilm main constituents of the humic acid and synthetic ferrihydrite were used as sorbent on the Wuhai sediment of Yellow River, comparative analysis the Wuhai section sediment of the Yellow River and after doping humic acid and ferrihydrite of Cd²⁺ adsorption characteristics. Discusses the adsorption time, various initial concentrations on Cd²⁺ adsorption onto sediments from Wuhai of Yellow River.The adsorption isotherms and adsorption kinetics were fitted and distribution coefficients were calculated. The results illustrated that the adsorption processes of sediments with different proportions of biofilm main constituents to Cd²⁺ were consistent with Langmuir adsorption isotherm curves (R²≧0.99,p≦0.02,n=7); Doping of humic acid and ferrihydrite on sediment, the distribution coefficients of Cd²⁺ were 6.2959 and 2.711, which were higher than the original (0.8626).

Abstract: Effects of initial pH on desorption of copper (Cu), cadmium (Cd), and lead (Pb) by different low molecular weight organic acids (LMWOAs) from soils were examined. Cu, Cd, and Pb removal by LMWOAs was highly dependent on the initial pH. With an increase in pH, the amounts of the three trace metals desorbed by malonic acid and DL-hydroxybutanedioic acid sharply decreased, and desorption of Cd and Pb by malonic acid followed the same trend. These results indicate that pH was the dominant factor governing the release of trace metals by LMWOA extraction. When the pH of the solutions was not adjusted, malonic acid was found to be most effective in extracting Cd and Cu from the field soil. Desorption of both Cu and Cd from soil followed a descending order (malonic acid >citric acid > DL-hydroxybutanedioic acid) that was consistent with the acids’ acidity from strong to weak. However, Pb desorption followed a release order (citric acid > malonic acid > DL-hydroxybutanedioic acid) that was well matched by the same sequence in the stability constants of their produced Pb-ligand complexes.

Abstract: Purpose The flow injection distillation (zinc acetate solution) was changed to be 5% phosphoric acid in the method of determination of cyanide. Application Cyanide in groundwater was measured by FIA6000 + automatic flow injection analyzer directly. Results In the 2.0-100.0μg/L range, the linear correlation coefficient was greater than 0.9, the recovery was 86.1% -100.8%, relative standard deviation 1.3% -3.8%. Conclusion This method not only reduces the white crystals [Zn (OH)₂] on the pump tube blockage, making the operation more simple and efficient, but also for the detection of a large number of groundwater samples.